November 12, 2012

Australian Sugar Ants Walk In Circles When Lost

For us humans, being lost isn´t all that much fun, often leading us to walk around in circles as we try to find our way. Apparently, some animals follow similar patterns.

Researchers studying Australian sugar ants have found that putting these social insects in an unfamiliar setting can immediately trigger a ℠lost´ reaction. Furthermore, their research shows that an ant´s habitat can determine how it navigates through its environment.

The team, from Australia´s Vision Centre, found that as ants travel from the nest to the food source, they use various clues to ensure they always know how to get home.

“One of those clues is recognizing familiar landmarks along their paths,” said study author Eliza Middleton, from The Vision Centre and the Australian National University. “They also count their steps to measure distances and use a ℠compass´ to monitor the position of the sun and the pattern of polarized light in the sky. A combination of these methods leads to path integration — a fundamental way used by ants and bees to always know the direct way home.”

To determine how these insects navigate, Middleton and her colleagues captured ants that were heading back to their nest and released them at a local site and also at a remote site. Middleton explained that the local site was well within the ants´ foraging range, while the remote site was in a completely unfamiliar setting.

“We then tracked them for seven minutes,” said Middleton in a media release.

“Previous research has shown that when ants are lost, they´ll use what they learned from path integration and go along the imagined route to where the nest should be, even if it isn´t actually there,” said the study authors. “We expected sugar ants at the remote location to do the same, since there weren´t any familiar landmarks, which meant that they had to fall back on path integration.”

But the sugar ants released in the remote setting did not adhere to previous studies. In fact, all ants placed in the remote setting walked around in circles for the full seven minutes the team tracked them. But those released at a local site, successfully found their way home, some following the ℠imagined´ route, managing to adjust their path along the way.

Middleton noted that this confirms that “ants at the local site used both path integration and landmark recognition to find their nest. As for ants at the remote site, their immediate switch to ℠search mode´ — walking around in circles — showed they knew they were lost, and that they completely ignored any path integration information.”

The findings show that sugar ants will use path integration in familiar sites, but totally disregard it when lost. It is possible that these insects were so overwhelmed by the new environment that they immediately tried searching for something familiar, hence walking around in circles, according to the team.

This behavior is not necessarily species-specific, but may be a result of foraging experience in a certain environment, according to Middleton. “Ants can use visual cues — such as landmarks — or path integration to go around, but whichever they pick as their primary method depends on where they live. Sugar ants behave this way because they live in the suburbs with lots of buildings, and in densely forested natural environments.”

Desert ants, which live in dense, landmark-rich habitats, would likely show similar patterns if they were to be placed in remote unfamiliar settings, noted the researchers.